If you think a Showtime series about pioneering sex researchers William Masters and Virginia Johnson guarantees plenty of salacious goings-on, peekaboo nudity and slap-and-tickle hijinks, well, "Masters of Sex" has some of that.

But, like the trailblazers whose story it tells, "Masters of Sex" -- premiering Sunday -- seduces and educates at the same time. One of the best new shows of the fall season, "Masters of Sex" effortlessly accomplishes something very difficult -- it takes the subject of human sexual behavior seriously, but also celebrates the fun and humor associated with what consenting adults do in the privacy of their own homes.

Possibly because four women are credited as executive producers (along with one man), "Masters of Sex" shows extraordinary sensitivity to the position women held in America in the 1950s. The writers and cast make it clear how much women were dominated by men, and expected to obey social rules about how they should behave. Break with those strictures by, for example, expressing your sexuality in an independent way, and you were likely to be punished, in any number of ways, from being denied promotions to being ostracized.

In addition, "Masters of Sex" is tremendously enjoyable, with fabulous mid-'50s costumes and production design, witty writing and situations that may make you blush, gawk or giggle.

In the pilot, written by co-executive producer Michelle Ashford and directed by John Madden, we meet Masters (Michael Sheen) a successful, respected OB/GYN on the faculty at St. Louis' Washington University. His marriage is strained by the difficulty he and his wife have in conceiving a child (the wife blames herself, though the truth lies elsewhere). But Masters is professionally fascinated by sexual response, and is engaged in after-hours research. And no, it isn't what you think.

"Masters of Sex" premiere

When: 10 p.m. Sunday

Channel: Showtime

Everything changes when Masters meets Johnson (Lizzy Caplan), a divorced single mother who has a guilt-free perspective when it comes to sex. Though hired as a secretary at the university, Johnson starts explaining some female sexual fundamentals to a clueless Masters. It soon becomes clear just how outdated his ideas are. And that's just the beginning. There's plenty that isn't accurately understood about male sexual response, also.

These two have their work cut out for them.

It must be noted that if you're squeamish about very frank discussion of male and female body parts, sexuality, and related matters, this isn't the show for you. There are scenes involving nudity and simulated behavior of various kinds that are strictly adults-only.

But beyond the eye-opening displays of flesh, "Masters of Sex" is genuinely enlightening. It helps that the cast is uniformly excellent. Sheen is playing an uptight, humorless know-it-all who is initially extremely hard to like. But even with all that, he makes Masters' scientific rigor and devotion to solving the mysteries of human sexuality admirable. Caplan is the heart and soul of the tale, at least in the early episodes, and her performance is warm, sensual and smart.

If you're familiar with the real-life story of Masters and Johnson, you know what's covered in the first few episodes is just the beginning of a long, complicated tale, one that continued into the 1960s and beyond. But it's a tale that changed Americans' lives. "Masters of Sex" makes you understand how.